This invention relates to the creation and generation of video test signals.
It is essential in the design, testing, maintenance and calibration of high quality video equipment to have access to precise test signals. The nature of the test signals that are required will vary widely from application to application and, whilst a large number of standard test patterns are available, there is a continual need for fresh test patterns to be created for specific applications.
Historically, the more complex test patterns were created optically and scanned whenever a test signal was required. More recently, digital test pattern generators have become available, and the more useful of these are programmable. Test signals are then created and stored as digital data files. The test pattern generator stores one or more such files and converts any one of them into a video signal corresponding to a stationary video test pattern or signal. A particularly useful form of test pattern generator is disclosed in WO-A-93/20659.
Software systems have been devised to simplify the creation of test signal data files. Existing systems may permit the user to specify the signal level at various sample sites along the video line or may allow him to construct a video line from a number of basic signal components such as sine waves, cosine.sup.2 pulses, colour bars and the like. Such systems may also allow the user to work at a terminal which displays a representation of the waveform enabling interactive amendment of the line signal. Once one or a number of line signals have been satisfactorily created, the corresponding data file is transferred to a test pattern generator and the test signal displayed on a video monitor. If the resulting test pattern is unsatisfactory, the data files can be re-loaded for editing in the software-driven creation system.
It will be recognised that the creation of a complex test pattern can be a time-consuming exercise even with the benefit of existing software tools.